Then Fine showed him this and asked him to identify it:
May studied the image.
“It’s a square with lines,” he said.
Those five words seemed the answer to Fine’s variation of Molyneaux’s question. She had asked whether the newly sighted man could distinguish a square from a cube. It appeared that May could not, even after six months of vision. All he saw was a square in two dimensions with extra lines.
For no particular reason, Fine pressed a button on the computer that put the shape in motion, rotating it in and out, in and out.
May shot up in his chair.
“That’s a cube!” he said.
Fine couldn’t believe what she was witnessing. Up to this point, she’d believed May to be virtually unable to see in three dimensions. Somehow, motion had produced in him the sensation of depth.
“That is absolutely incredible,” she said. “That was just the coolest moment I think a scientist could ever hope to experience. I don’t think I’m ever going to forget this, Mike. And I think it’s really important.”
That night, May and MacLeod went to dinner at the San Diego condo where Fine and Boynton lived. Before May arrived, Fine told Boynton about the day’s fascinating test results, and about how frustrated her subject seemed when trying to perceive faces. Fine worried—she was a laboratory scientist and had no experience in helping people deal with stressful situations. Living in such a confusing visual world had to be frightening. She wished she knew how to help.
Fine served wine and cheese when May arrived. The conversation surfed from baseball to graduate students to local politics.
“Anyway, Mike,” Fine said during a brief lull, “how’s it going? How are you feeling?”
“I’m fine,” he said. “But I’m curious about something, Ione. Why do you keep asking if I’m okay?”
“Umm…uh…umm…”
Fine could not find the words. She looked to Boynton for an assist. None was forthcoming.
“Well,” she said finally, “it seems like there’s a high incidence of depression in other sight-recovery subjects. We just want to make sure you’re okay. We don’t want to push you on this stuff.”
May smiled. “Don’t worry about me,” he said. “I thrive on pushing. Push away.”
Fine said that she’d been telling Boynton and MacLeod about the results of the face testing.
“Did she tell you I stunk?” May asked.
They confirmed that she had.
“It’s really a mystery to me,” May said.
“Do you know that perhaps one in a hundred people in the general population—maybe even more—can’t recognize faces?” Boynton asked. “They can’t even recognize the faces of people they know and love intimately.”
“What do you mean? Why not?” May asked.
“It’s a condition called prosopagnosia, or ‘face blindness.’ It’s thought to relate to a problem in the part of the brain that does a lot of face processing. You don’t hear much about it because often people are embarrassed to talk about it, and others don’t even know they have it.”
“How can a person not know they have it?”
“Because those people have always used other clues to recognize people, like a person’s walk, hair color, clothes, that kind of thing.”
“That’s what I use. Do you think I have this condition?”
“You do have prosopagnosia, but it seems to be part of a more general difficulty in understanding the visual world. In most people with prosopagnosia, their problems are limited to faces. Yours seem to go way beyond faces.”
The conversation turned to the subject of facial beauty. What was it, May wondered, that made a person’s face beautiful? He’d forever heard about the mysterious allure of the eyes, the drama of high cheekbones, the power of a strong chin. But what did all that mean?
He couldn’t understand those things even when he got close enough to see them.
Fine, MacLeod, and Boynton told him that researchers believed that attractiveness in faces seemed to be based on two factors.
The first was symmetry—people seem to prefer faces that are as closely matched as possible on the left and right sides. There might be evolutionary value in choosing such a person, since symmetry provides evidence that the person has good genes and that everything went right during early development.
The second was averageness—people seem to like faces that are the average of their gender. If one were to average the features on, say, one thousand female faces, the result would be a slightly pixieish woman that nearly everyone in the culture would find pleasantly attractive (though few would find gorgeous). It would work the same for male faces.
“But isn’t beauty a cultural thing?” May asked. “There was a time when men preferred a Rubenesque woman. Now they prefer a thinner build. Maybe it’s just the culture of the time.”
“Ah, but the waist-to-hip ratio stays constant,” Fine countered. “You can have a society that likes thin women or plump women, but men seem consistent in their preference for a .67 waist-to-hip ratio, or thereabouts. Essentially, that means the woman’s fertile.”
“What’s your ratio, Ione?” Boynton asked.
“A lady never reveals her ratio,” Fine said. “But I will tell you that when I was in graduate school and heard about this waist-to-hip thing, I ran right home from class and measured. And I was right there at .67. I was very proud of myself.”
They talked long past dinner. May savored the conversation. And he liked these people. In their tone, in their laughter, and in their ease, he could hear that they wanted more than just to study him. He could hear that they wanted the best for him.
May was scheduled to fly home the next morning. Fine brought him to her lab for a few quick tests before his flight. In her office, she became annoyed by the swirling and bouncing patterns of the screen saver on her monitor.
“That is incredibly distracting!” she said, sliding her chair toward the screen and turning it off.
“That’s how vision feels to me all the time,” May said.
Fine’s last tests were on visual illusions. May’s reaction to one of them struck her as particularly illuminating. She showed him these two tables:
To normally sighted observers, the tabletops appear to have entirely different dimensions. To May, they appeared identical. May was correct—the tables are made from identical rectangles. He did not perceive the illusion.
May could hear Fine writing notes. Occasionally, she would murmur something to herself. He could sense her putting together the strange nature of his case, connecting the results and sorting the ambiguities to form an explanation, and maybe even a prognosis. Yet he did not want to push her for answers. “She’ll tell me when she’s ready,” he thought.
On the way to the airport, Fine told May a bit more about growing up in Scotland as the daughter of a philosopher and a famous children’s book writer. Her name, she said, appeared in some of her mother’s books. Certain that Fine was pretty, May wanted to look at her more closely in the bright sunlight of the car, but he feared getting busted, so mostly he looked straight ahead.
As they neared the airport, Fine asked if May was willing to do some follow-up testing—he could return to San Diego or she could travel to Davis.
“Either way,” he said. “I’m game.”
At the terminal, she thanked him for his time and for being such a good sport during the tests. She told him how unlikely—impossible, really—it was for a scientist to find such a rare case as his, and such a bright and willing subject. She called it “once in a lifetime,” and May knew what she meant. It was how he had come to think of his encounter with Dr. Goodman, the adventure he’d undertaken over the last five months, and about his feeling for these scientists in San Diego who were trying, with a few ghosts from history as their guides, to understand him.
May went back to work the same day he returned from San Diego. At night, he told Jennifer and his kids about his tests, about Fine, and a
bout the idea that the scientists might put together some interesting theories about his case.
“And remember this,” he warned his kids. “I don’t fall for illusions. So don’t try to pull any fast ones.”
The next day he told his friend Bashin about the tests. Bashin couldn’t get enough of the information.
“It’s even more fascinating than we realized,” Bashin said. “What’s their thinking on this?”
“They haven’t told me yet,” May replied. “I think they’re still trying to figure me out.”
In San Diego, Fine tested a control group of subjects on the same tests she had given May. She removed the detail to simulate May’s low acuity. They still got everything right. They still perceived illusions. That meant May’s results were not due to poor acuity. They were due to something else.
Fine kept puzzling over May’s case. He could perceive motion beautifully but was shockingly bad at other critical aspects of vision. Late one night, she wrote an e-mail to MacLeod:
I keep thinking about Mike suddenly seeing the cube in depth when it was put in motion. It’s a little like the way a cat chases a ball of string when it’s moving. Maybe Mike has a cat brain? Am I going crazy?
She was horrified a moment later to realize she’d sent the e-mail to May rather than to MacLeod. She received a reply a few minutes later.
Glad to know I have a cat brain. Must go out for cat food now. Mike.
In subsequent discussions, Fine and MacLeod came to think of May’s visual world as much like an abstract painting, filled with colorful and mostly flat and meaningless shapes. When people asked what Fine thought it was like for May to see, that was the best description she could give—that it was like looking at an abstract painting, that he had Picasso eyes.
Except when things moved. Motion, it seemed, lent a sense of depth to May’s visual world.
Over the next several weeks, May traveled to San Diego and Fine traveled to Davis for more testing. The results were always the same: he was excellent at motion and color, terrible at understanding faces, seeing in depth (except if something was moving), and recognizing objects.
To May, this dichotomy remained as mystifying as ever. To Fine, however, it was all starting to fall into place. As she further contemplated the test results, reviewed cases that dated back to the 1700s, and lay awake at night thinking, she began to understand not just why May saw the way he did, but about the implications for his future, about whether he might improve. Her insights were grounded in a new way of thinking about how vision works—a way of thinking that just a few scientists were beginning to explore.
CHAPTER FOURTEEN
Before the middle of the nineteenth century, vision was widely thought to be a passive experience, one in which objects were simply “out there” to be seen. Various explanations were put forth to describe the process, including the idea that the eye shot “fingers” of light onto objects in order to “touch” them, or that objects broadcast images of themselves to the observer. These accounts supposed the world and its objects to be self-evident; seeing them did not require the brain to make inferences or engage in problem solving or do any of its usual cognitive work. And that made sense. Seeing felt effortless and automatic, if it felt like anything at all.
But then, starting in 1850 with the renowned German scientist Hermann von Helmholtz, and continuing in the middle of the twentieth century with psychologist Richard Gregory and others, scientists offered a startlingly different explanation for the brain’s role in vision. Human beings, they argued, depended to a great extent on knowledge in order to see, to make sense of what Gregory called the “shadowy ghosts” that were the retinal images in our eyes.
The idea seemed preposterous on its face. How could knowledge make it possible to see? Surely, the most uneducated person saw as well as the most learned. But Helmholtz, Gregory, and the others were not referring to a knowledge of facts and figures of the kind found in encyclopedias. By knowledge, they meant a set of assumptions about the world and the objects that exist in it. This set of assumptions, they argued, was so deeply ingrained in the human brain that people imposed them instantaneously, automatically, and unconsciously on the visual data streaming in from the eyes. No one realized they were using knowledge to interpret the visual scene, but everyone did it all the time.
There was powerful evidence to support this theory. Among the most compelling examples was the existence of visual illusions. If objects were simply out there to be seen, visual illusions wouldn’t occur—people would see things properly, as they actually were. Yet there were numerous visual illusions. What caused them?
Gregory and others argued that many visual illusions resulted when a person’s implicit knowledge—that instant, automatic, and unconscious set of assumptions about the world and its objects—dominated over contrary evidence from the eye.
The hollow face illusion provides a powerful example of this dynamic. It can be demonstrated by showing an observer the front of a simple plastic Halloween mask—say, one of Charlie Chaplin. As expected, the observer sees the face as convex—Chaplin’s features protrude outward. When the mask is rotated to show the reverse side, however, Chaplin’s hollow features also suddenly appear to protrude outward; they look as robust and convex as they did when viewed from the front.
What explains this illusion? Gregory argued—and every vision scientist now agrees—that it is due to the observer’s very powerful knowledge of faces: every face he has ever seen has been convex. Therefore, despite the visual evidence, he must perceive the hollow face as pointing outward. His implicit knowledge of faces is so powerful that he cannot defeat the illusion—even if he consciously tells himself that he is seeing a hollow face.
Consider another illusion, “Terror Subterra” by Roger Shepard. Which monster in the picture is larger?
Nearly all observers perceive the monster in the rear to be much larger. In fact, they are identical in size—hold your finger against the picture to check. Again, the role of knowledge—one’s set of assumptions about the world and its objects—is critical to the perception. But what knowledge causes us to perceive one monster as so much larger than the other?
In human experience, an object’s perceived size depends on two factors:
• Its size on the retina
• Its perceived distance
That makes for a simple formula:
Perceived size=size on the retina × perceived distance
If these monsters were the same size, the one that appears farther away should cast a smaller image on the retina. Since it doesn’t, the brain hypothesizes that the more distant monster is larger than the closer monster. And that hypothesis is so strong that the observer truly sees it that way.
But that’s not the only bit of knowledge the brain imposes on this scene. Look at the monster’s faces. The one being chased appears terrified. The one doing the chasing appears aggressive or angry. In fact, their faces are identical. In human experience, people being chased almost always appear frightened, while people doing the chasing almost always appear aggressive or angry. Our brain imposes that knowledge on the scene and therefore “sees” what it expects to see. (Illusions like this can even be affected by the particulars of our own experience—children of abusive parents, for example, are more likely to see a neutral face as angry, even at a very early age.)
This idea—that knowledge and vision are highly related—can be demonstrated in myriad examples that do not involve visual illusions. What do you see in this picture?
Some observers see a duck; others see a rabbit. Then the perception quickly shifts—those who saw the duck now see the rabbit, and vice versa. The brain’s knowledge of these animals—its assumptions about them—causes it to form two hypotheses about the image. Since each hypothesis is equally likely, the brain continues to entertain them both, resulting in the “flipping” of vision between duck and rabbit. (Note, however, that if an observer is told beforehand that he will be viewing a picture of a duck,
it is unlikely that he will first see the rabbit. In that case, the brain has been given some extra knowledge that it will bring to bear on the picture, and this will dominate what is seen.)
Recent advances in the ability to measure specific kinds of brain activity confirm that knowledge and vision are highly related. It is now thought that more than a third of the human brain is involved with vision, an indication of the magnitude of the task. Today, it is virtually impossible to find a vision scientist, researcher, or psychologist who does not agree that knowledge and vision are highly related, and that without our knowledge about the visual world our ability to understand visual scenes would fall apart.
This current understanding of vision seemed to have great implications for May’s case. If knowledge and vision are highly related, and there’s nothing wrong with May’s eye, it seemed distinctly likely that May had a knowledge problem.
To get at the nature of such a problem, we must understand how human beings come to attain this knowledge in the first place.
A newborn’s eyes are flooded with visual information—colors, motion, and shapes that come from objects in the world around it. Yet newborn babies have no experience with any of these things, and few assumptions about them.
What must it be like to see things about which you have no experience or knowledge? We can scarcely imagine it—by adulthood, we have experience with nearly everything. If we do experience something completely foreign to us, we find it nearly impossible to impose a meaning or interpretation on the image.
Crashing Through Page 24
